Abstract

Sea hares, Aplysia californica, are opisthobranch gastropods found in the coastal, temperate waters from Northern California to Baja California, Mexico that are widely used for studies of neurobiology.^1,2,3,4 Vibriosis and other microbial infections could potentially have a devastating effect on a laboratory population of animals and pose a threat to human caretakers.⁵ There are no approved drugs for use in Aplysia or other mollusks in the United States. Because the fluoroquinolone enrofloxacin has a lower prevalence of antibiotic resistance in Vibrio sp., it was selected for this study.^6,7,8

Six juvenile Aplysia californica were individually identified and group housed in an open seawater flow system at 14–18°C. At each time point after enrofloxacin dosing at 5 mg/kg, 300 µl of hemolymph was collected as shown (Figure 1). Samples were analyzed via HPLC-UV for enrofloxacin and ciprofloxacin. Pharmacokinetic parameters that were calculated using non-compartmental analysis included area under the curve (AUC), mean residence time (MRT=area under the first moment curve (AUMC)/AUC), total body clearance (CL=Dose/AUC), volume of distribution at steady state (Vdss=CL*MRT), Cmax (the peak concentration) Cmax/MIC and AUC/MIC.

All Aplysia immediately recovered post-manipulations. Enrofloxacin, but not ciprofloxacin, was detected in all dosed animals at an average peak concentration of 3 µg/mL (therapeutic range is 0.18–0.63 mg/ml)^7,8 and remained in the body for 20.3 h with an average clearance of 0.19 mcg*h/mL. The MRT was approximately 26.6 h and mean half-life was 18.4 h. Hemocoel injection of enrofloxacin appears to be an effective way to administer enrofloxacin to Aplysia.

This research is recently published in JAALAS.⁹

Acknowledgements

We would like to thank Delta Dise, North Carolina State University College of Veterinary Medicine for her assistance in analyzing samples in this analysis and Mal R. Hoover, Certified Medical Illustrator, Kansas State University College of Veterinary Medicine for the original illustrations. This research was supported by the NIH/National Resource for Aplysia at the University of Miami, FL, PHS Grant P40 OD010952 and Geraldine R. Dodge Foundation welfare for animals.

Authors declare competing interests. Dr. Papich has received consulting fees, honoraria, and research support from Bayer Animal Health, the manufacturer of enrofloxacin.

Figure 1 is included in this abstract with the permission of the American Association of Laboratory Animal Science.

* Presenting author

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